Adam J

Great image, As you say the issues are more with the duo-band filters though. Adam

Green and Blue fringing is an odd one, you would normally expect Red / Blue if it was something like a decentered lens element. You should be able to see this in each of the RGB stacks as a change in the shape of the star between each channel, like coma but shifting direction from red to blue. If I split out the green channel in PS I do kinda see a little of that with the a tiny bit of something left of the red and to the right of the blue and the green being correct, but its more in the halo than anything else. Its also notable that this is seen across the entire image in the same orientation and so is not typical lateral CA (usually caused by a corrector in any case and you are not using one), there are a few other things it could be though. Its almost like there is a flare on the top left of the Red channel and if you removed that then it would look quite similar to the blue. So all in all I would not panic right away as there could be something else going on here. 1) RGB, 2) RB, 3) R, 4) G, 5) B: You dont say if the camera is an OSC 428 or a Mono 428? You mention a filter wheel so am guessing mono. Also if you are using filters, what filters are you using / what brand size etc? Red and Blue, filters not sitting flat in the wheel could cause this kind of effect. What order did you shoot the RGB in? The flair in red could be as a result of the scope not being fully cooled down (for that matter the whole thing could be that). Two things to try here are to rotate the entire imaging train relative to the primary (use a shim so it tightens in a difference spot or the rotator if the scope has one) if the aberation remains fixed relative to the camera then its not the primary, if the aberation rotates as you rotate the camera it becomes more likely its the scope optics. The other thing to do it to perform a star test (try and get an image with between 3 and 5 diffration rings in each RGB channel). It could be a simple colimation error and that will show up on the star test. In any case dont be tempted to try and mess about with the lens centring yourself. All in all I would be better off taking a look at the linear stack for each channel as opposed to splitting an RGB image. The other thing you could do is just forget about it and move on as for me it is not detracting greatly from the image when viewed at a reasonable scale and you are pushing the saturation quite hard for limited SRN. Adam

Dark flats too as it will likely change your exposure time.

Those settings are in DSS not the camera.

another issue may be the debayering settings, if those are not correct star detection will not work. Adam

What camera was the FSQ using? Very Nice.

Not really sure it would offer a significant advantage with the DSLR, especially not anything that is half modern. Adam

How was your focus?

The pattern is certainly present on the mono version and I don't see why it would be different in terms of linearity / saturation. What i would say is that it was odd that Sony gave the mono version of the IMX294 a new designation IMX492, see what they did there as opposed to every other chip they make which retains the IMX designation from OSC to mono.....so perhaps something else was tweaked apart from removing the Bayer matrix? As the issue is worst in duel narrow band filters it may not be as heavily reported as you would not use such a filter on a mono camera. But then again those who have used a pure Ha filter on a OSC 294 have reported calibration issues. Personally I have determined that I wont be spending £1500 to find out first hand for myself. https://www.cloudynights.com/topic/762898-mottling-in-asi294mm-image-and-flats/page-2 Adam

looks like a trick of perspective to me.

I think the reason for the pattern and the reason why its not calibrating correctly are two different issues. The pattern means that calibration errors are very apparent but the pattern in itself is not the cause of the calibration errors, the cause of the calibration errors is non-linearity of the sensor response with exposure. and failure of the sensor to fully saturate at specific gains. Maybe @PadrePeace can comment on the results at Gain 200 in comparison to gain 121. Adam

I have seen it effecting many 294 cameras, its caused by a combination of a fixed pattern that changes from camera to camera and can be variable in severity and the slight none linearity of the sensor in that gain window. Also if you have sufficient LP then you can swamp the issue. Extensive discussion around this on cloudy nights and some on the sharp-cap forums. But yes some will see it more than others, always something there and you can removed it with skilled use of a dynamic background extraction. The effect is most obvious when the camera is used with Narrow band filters. Adam

You EEVA chaps must be delighted with the announcement of the non-cooled ASI533mm camera?

Its worse than that, in addition to the early saturation there is evidence its non linear for gains between 120 and 190 and that really messes with calibration. A friend has recently had more success with flats at gain 200. Adam

I have an esprit 100, as above I would use the 533 along side a Riccardi reducer x0.75 or a Apex-L reducer x0.65 to get a wider FOV from it. It would also mean that unlike the 294 I would be able to keep using my expensive AD filters which are only 1.25 as they would not work with the 294 and especially not at F3.5 with the Apex L. Apart from that its just a cleaner sensor and the 294mono can have some calibration issues along the same lines of those people experience with the 294 OCS version, with a factor being sample to sample variation. Its very similar to the KAF8300 vs Sony ICX694 debate from the late CCD era. Adam

No it is a real issue as if you had to do more panels then you are effectively slowing down your data gathering as you now need to do maybe 50% more exposure time. The 294mm (IMX492) is not so good a sensor as the 533 and so if your target fits on the 533 sensor or requires the same number of panels then you are likely better off with the 533. Adam

I hear lots of people saying things like its not 16bit and I dont like square sensors. For astronomy, but probably nothing else I actually like the square format easy life in terms of vignetting / flat feild / framing. This sensor would allow me to reduce my Esprit 100 to F4 or even less using something like the APEX-L with my 1.25 inch Astrodons and have no vignetting for example, saves a significant amount on filters and allows for fast optics. As for the 16-bit thing, that really has very very little advantage over 14-bit to the point that I would call it insignificant. It really is a strong contender, just so long as they price it closer to the 183 than the 1600 and certainly nothing close to the 294mono. Am hoping for around £1050...if ZWO go too high then I have no problem going to QHY. Adam

Also hence why debayering algorythems tend to weight the green channel (as a relative measure) when interpolating the luminance of each colour channel. But that may be what you are trying to say above.

Its essential to dither every frame if you are going to use drizzle. That can be expensive in terms of time and the SNR will be decreased if bayer drizzle is used.

More than that as the QE of the camera can be significantly more in the Green than Blue or even Red.

Pritty much what vlaiv says, everything else has had amp glow so far or high dark current and you really do need stable temps for that to work. Certainly if you had a RASA at F2 then I would think that there would really be no need for the cooled version, you could easily use 30s - 60s narrow band exposures at high gain even in 20c ambient. Not sure if anyone had every tried the OSC version without cooling but it would be a good test if someone wanted to do it. If it came in at under 700 pounds, ideally closer to 600 then a triple RGB / SHO imaging rig using 3 x ASKAR FMA180s for mobile work would be something i would consider. Adam

Well that is very very interesting as in theory it may not need cooling in milder climates..... Certainly if ambient was 10c there would be little benefit in cooling for subs even upto 5mins. Adam

Not a bad option....

What ever happened to these FLO? Adam

Yes its a duel axis goto version of the star-adventurer that has been banded about. But you never know with Sky-watcher they announced an entire range of telescopes in the form of the EVOLUX a couple of years back with a flyer like that one. Those never materialised at all. I say because i see those same scopes mounted in that picture. some places even let you pre-order them lol. Adam